Virgin River Restoration, Ecohydrological Assessment

Stillwater Sciences is an active participant in a collaborative science team developing a restoration framework for the flood-prone, ecologically sensitive Virgin River. The overarching goal of the Restoration Framework is to promote removal of non-native tamarisk (salt cedar) and recovery of native riparian habitat. The primary focal species is the endangered southwestern willow flycatcher, with additional concern for yellow-billed cuckoo, Yuma clapper rail, Virgin River chub, and woundfin. As part of this effort, Stillwater is conducting an Ecohydrological Assessment to identify sustainable restoration sites and prioritize cost-effective restoration actions, while simultaneously building the capacity of local communities to support and participate in achieving restoration success.

The challenges inherent to any such restoration effort are compounded by two additional factors: (1) the recent establishment and success of the tamarisk leaf beetle—an introduced biological control measure for tamarisk—has impacted flycatcher nesting habitat in tamarisk-dense areas, and (2) large flood events have repeatedly shifted the active channel path and scoured riparian vegetation: both invasive tamarisk and native riparian species stands, as well as recently implemented riparian restoration throughout the river. The dynamic nature of the system, coupled with multiple biological and ecological targets and goals, illustrates why a sound ecohydrological assessment to identify areas where restoration will be sustainable and least susceptible to flood-induced disturbance is critical to ensure success.

Synthesizing our flood-scour mapping with vegetation-type mapping has highlighted numerous suitable restoration locations along the 130-mile river corridor. At the sub-reach scale, we have considered additional environmental factors: groundwater, soils, bed-elevation changes, land-uses, and other wildlife needs. This work is currently assisting the multitude of watershed managers in development and prioritization of appropriate restoration strategies.

Overview

Location
Washington County, Utah; Mohave County, Arizona; and Clark County, Nevada

Funding Source
Walton Family Foundation Freshwater Initiative Program and The Nature Conservancy in Utah

Work Products

IMAGE

Stillwater is completing an ecohydrological assessment of the Virgin River to help prioritize restoration actions within the river corridor, which includes enhancing habitat for the southwestern willow flycatcher (flycatcher photo courtesy of R. Fridell, Utah Division of Wildlife Resources).